Device and method for monitoring an electric current in a power converter, power converter device

Abstract

The invention relates to the monitoring of an electric current in a power converter, for example a DC-DC converter. For this purpose, a transformer is provided, which is coupled into a current path of the power converter on the primary side. Sensor signals corresponding to the mean value and / or a peak value of the current flow to be monitored can be provided on the secondary side of said transformer. For this purpose, an electrical connection between the secondary side of the transformer and the outputs of the sensor signals is opened when the primary side of the transformer is not energised. During these time intervals, the transformer can be demagnetised in order to compensate for a DC voltage offset in the current to be monitored.

Description

[0001] Description

[0002] title

[0003] Device and method for monitoring an electrical current in a power converter, power converter device

[0004] Technical area

[0005] The present invention relates to a device for monitoring an electrical current in a power converter. The present invention further relates to a power converter device having such a device for monitoring the electrical current. The present invention further relates to a method for monitoring an electrical current in a power converter.

[0006] background

[0007] Power converters, such as DC-DC converters, are capable of converting electrical energy from a power source at a first voltage level and a first voltage waveform and outputting it at a desired second voltage level with the same or a different voltage waveform. For example, a DC-DC converter can be used to convert an input DC voltage into another DC voltage with a higher or lower electrical voltage.

[0008] If necessary, the voltage waveform can also be modified, so that, for example, an input DC voltage is converted into an output voltage in the form of a single- or multi-phase AC voltage. The power converter can also be designed with galvanic isolation, so that the input voltage and the output voltage are galvanically isolated from each other.

[0009] Power converters can be unidirectional, meaning electrical energy is transmitted in only one direction. Alternatively, bidirectional power converters are also available, allowing electrical energy to be transmitted in both directions between the power converter's terminals.

[0010] The document DE 10 2016 200 662 A1, for example, describes a bidirectional DC-DC converter for energy transmission between a low-voltage network and a high-voltage network in an electric vehicle.

[0011] Disclosure of the invention

[0012] The present invention provides a device and a method for monitoring an electrical current in a power converter, as well as a power converter arrangement having the features of the independent claims. Further advantageous embodiments are the subject of the dependent claims.

[0013] Accordingly, it is provided:

[0014] A device for monitoring an electrical current in a power converter. The power converter is designed to be coupled to a first energy supply network at a first connection. Furthermore, the power converter is designed to be coupled to a second energy supply network at a second connection. The device for monitoring the electrical current in the power converter comprises a transformer, a demagnetization device, and a switching element, in particular a bidirectional switching element. The transformer comprises a primary side and a secondary side. A first connection point of the primary side of the transformer is electrically coupled to a connection point of the first connection of the power converter. A second connection point of the primary side of the transformer is electrically coupled to a connection point of the first energy supply network.Another connection point of the power supply network can be electrically coupled to a second connection point of the first connection of the power converter. The connection points of the second connection of the power converter can be coupled to corresponding connection points of the second power supply network. The demagnetization device is arranged between a first connection point and a second connection point of the secondary side of the transformer. The demagnetization device is designed to allow an electrical current to flow between the first connection point and the second connection point of the secondary side of the transformer if an electrical voltage between the first connection point and the second connection point of the secondary side of the transformer exceeds a predetermined threshold.The switching element of the device for monitoring the electrical current is arranged between the first connection point of the secondary side of the transformer and a reference potential. The device for monitoring the electrical current is particularly designed to provide a first voltage signal corresponding to a peak value of the electrical current to be monitored in the power converter. Additionally or alternatively, the device for monitoring the electrical current is designed to provide a second voltage signal corresponding to an average value of the electrical current to be monitored in the power converter.

[0015] Furthermore, a power converter arrangement comprising a power converter and a device according to the invention for monitoring an electrical current in the power converter is provided. The power converter is designed to be coupled to a first power supply network at a first terminal and to a second power supply network at a second terminal.

[0016] Finally, it is planned:

[0017] A method for monitoring an electrical current in a power converter of a power converter arrangement according to the invention. In the method, the switching element in the device for monitoring the electrical current in the power converter is alternately closed and opened. In particular, the switching element is closed when the primary side of the transformer is energized and opened when the primary side of the transformer is not energized. The method further comprises a step for providing a first voltage signal for detecting a peak value of the electrical current to be monitored in the power converter. Additionally or alternatively, the method can comprise a step for providing a second voltage signal corresponding to an average value of the electrical current to be monitored in the power converter.

[0018] The power converter can basically be any power converter that can transfer electrical power between a first terminal and a second terminal. For example, the power converter can be a DC-DC converter that can transfer electrical power between a first DC terminal and a second DC terminal. However, power converters that can transfer electrical power between a DC terminal and a single- or multi-phase AC terminal are also possible. The power can be transferred unidirectionally, i.e., in principle, only in one direction from the first terminal to the second terminal, or bidirectionally, i.e., from the first terminal to the second terminal and from the second terminal to the first terminal.

[0019] In particular, the power converter may be a galvanically isolating power converter. For this purpose, a transformer or similar device may be provided within the power converter to ensure galvanic isolation between the first and second terminals.

[0020] The voltage level at the first terminal of the power converter can differ from the voltage level at the second terminal. For example, the voltage at the first terminal of the power converter can be lower than the voltage at the second terminal. Likewise, the voltage at the first terminal of the power converter can be higher than the voltage at the second terminal of the power converter.

[0021] Reliable monitoring of the electrical current in the power converter can be of great importance for the monitoring and operation of power converters, and in particular for protective measures such as emergency shutdown in a hazardous situation. For this purpose, it may be particularly desirable to provide a potential-free sensor signal that corresponds to an electrical current in the power converter. However, if transmitters or transformers are used for galvanic isolation to provide potential-free sensor signals, electrical currents subject to a DC voltage offset pose a significant challenge.

[0022] It is therefore an idea of ​​the present invention to take this finding into account and to create a concept for monitoring an electrical current in a power converter, which enables the reliable and precise provision of potential-free sensor signals for an electrical current in a power converter. For this purpose, the primary side of a transformer is integrated into the current path of the power converter and, with the aid of a suitable switching element, only those time intervals are taken into account on the secondary side of this transformer in which the primary side of the transformer is energized, while in the remaining time intervals, magnetization in the transformer can be reduced by means of a suitable demagnetization device. In this way, even electrical currents with a DC voltage offset can be reliably and correctly detected.The inventive circuit concept for monitoring the electrical current in the power converter enables very short response times for detecting current peaks, even at high switching frequencies of the power converter. This allows for the required shutdowns to be carried out very quickly in the event of a fault or danger, thus protecting, among other things, the affected semiconductor components in the power converter from possible damage or overload.

[0023] According to one embodiment, the switching element in the device for monitoring the electrical current is designed to be closed when the primary side of the transformer is energized. Furthermore, the switching element is designed to be opened when the primary side of the transformer is not energized. Thus, current only flows through the switching element on the secondary side of the transformer when current is energized. During the remaining time intervals, magnetization in the windings of the transformer can be reduced by the demagnetization device. This clocked opening and closing of the switching element can prevent the measurement result from being affected by the current flowing during demagnetization. The switching element conducts the current in both directions when it is closed and blocks the current in both directions when it is open.

[0024] According to one embodiment, the device for monitoring the electrical current comprises a first measuring resistor. This first measuring resistor is arranged between the reference potential and the first connection point of the secondary side of the transformer. Thus, a voltage signal can be provided via this first measuring resistor, which corresponds to the current flow in the power converter and from which, in particular, a sensor signal for detecting the peak value of the electrical current in the power converter can be derived.

[0025] According to a further embodiment, the device for monitoring the electrical current comprises an electrical low-pass filter. The low-pass filter is arranged between the reference potential and the first connection point of the secondary side of the transformer. Such a low-pass filter can be used to obtain a sensor signal that corresponds to an average value of the electrical current in the power converter. The low-pass filter can be formed, for example, from an electrical resistance and a capacitance.

[0026] According to one embodiment, the device for monitoring the electrical current comprises a reference voltage source. The reference voltage source is designed to provide an adjustable offset voltage. The reference voltage source can be coupled to the second connection point of the transformer via a voltage divider.

[0027] Additionally or alternatively, the reference voltage source can be electrically coupled to an output terminal of the low-pass filter via a second resistor. Such a reference voltage source can be used to apply an offset to the sensor signals for the electrical current in the power converter. In this way, a positive sensor signal can also be provided for negative currents, i.e., for a power flow from the second terminal to the first terminal of the power converter.

[0028] According to one embodiment, the switching element comprises two complementary semiconductor switching elements connected in series. The two series-connected semiconductor switching elements can be switched via a common control signal. The complementary arrangement of the two semiconductor switching elements allows for reliable interruption of the electrical connection regardless of the polarity of the applied voltage.

[0029] According to one embodiment, the demagnetization device comprises two Zener diodes arranged in series opposite one another. When the switching element is open, an electric current can flow through these Zener diodes to demagnetize the windings of the transformer. In this way, magnetization in the transformer can be reduced while the switching element is open.

[0030] According to one embodiment, the switching element is designed to be controlled using a control signal from the power converter. In particular, a control signal for the switching element can be obtained from the gate signals for switching transistors in the power converter. In this way, the switching operations of the switching element can be synchronized with the switching operations in the power converter. The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention described previously or below with regard to the exemplary embodiments that were not explicitly mentioned. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0031] Short description of the drawings

[0032] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0033] Fig. 1 : a schematic representation of a basic circuit diagram of a power converter arrangement with a device for monitoring an electrical current according to an embodiment;

[0034] Fig. 2: a schematic representation of a basic circuit diagram for a device for monitoring the electrical current in a power converter according to an embodiment;

[0035] Fig. 3: Timing diagrams illustrating the switching behavior and the course of the sensor signals, as they can be used to monitor the electrical current in a power converter according to one embodiment; and

[0036] Fig. 4: A flowchart illustrating a method for monitoring an electrical current in a power converter according to one embodiment. Description of Embodiments

[0037] Figure 1 shows a schematic representation of a basic circuit diagram of a power converter arrangement with a device 1 for monitoring an electrical current in a power converter 2. In the embodiment shown here, the power converter 2 is a DC-DC converter, in particular an active clamp flyback converter. However, this power converter 2 is only to be understood as an example and is not intended to represent a limitation of the present invention. In principle, any other suitable power converters, in particular clocked power converters, are also possible. Such a power converter 2 can transmit electrical energy between a first energy supply network 3 and a second energy supply network 4.The power converter 2 can enable unidirectional energy transmission, i.e., energy transmission in only one direction, for example, from the first energy supply network 3 to the second energy supply network 4. Alternatively, bidirectional power converters 2 are also possible, which can enable energy transmission from the first energy supply network 3 to the second energy supply network 4 as well as energy transmission from the second energy supply network 4 to the first energy supply network 3.

[0038] In the case of a DC-DC converter 2 illustrated here, the first power supply network 3 and the second power supply network 4 can each be DC voltage networks. However, for power converters in the form of an inverter, one of the power supply networks 3, 4 can be a single-phase or multi-phase AC voltage network. The voltage levels in the first power supply network 3 and the second power supply network 4 can differ from one another. For example, the voltage level of the first power supply network 3 can be lower than the voltage level in the second power supply network 4.

[0039] The power converter device with the line converter 2 can be used, for example, to couple a low-voltage network and a high-voltage network of an electric vehicle. For example, the first energy supply network 3 can be the high-voltage network of such an electric vehicle, and the second energy supply network 4 can be the low-voltage network of the electric vehicle. In this case, the voltage level in the low-voltage network can be, for example, in the range between 12 and 50 volts, in particular 12 volts, 24 volts, or 48 volts, while the high-voltage network has an electrical voltage of several hundred volts, for example 350 to 400 volts, 800 volts, or 1000 volts.

[0040] As shown in Figure 1, the power converter 2 can comprise a transformer 25. Using such or a similar component, it is possible to realize galvanic isolation between the first energy supply network 3 and the second energy supply network 4. Furthermore, one or more switching elements, in particular semiconductor switching elements 21 to 24, can be provided in the power converter 2. This makes it possible, for example, to supply clocked current to one side of the transformer 25. Likewise, the switching elements, in particular the semiconductor switching elements 21 to 24, can be used to rectify an output voltage or an output current from the transformer 25. Furthermore, one or more capacitors 20, 27 and, if necessary, other suitable components can be provided in the power converter 2.The switching elements 21 to 24 in the power converter 2 can be controlled and thus opened or closed by providing suitable control signals, in particular gate control signals. The provision of such control signals can be realized, for example, by a control device not shown here. Since the switching principle of power converters and also the methods for controlling or timing the switching elements in such power converters are considered known, further explanation is omitted here.

[0041] A device 1 for monitoring an electrical current can be provided between a connection point 3a of the first energy supply network 3 and a corresponding connection point 2a of the first terminal 28 of the power converter 2. Such a device 1 can monitor the electrical current flowing between the first energy supply network 3 and the power converter 2. This can also provide information about the electrical current flowing between the power converter 2 and the second energy supply network 4. If the voltage level is known, the power flow between the first energy supply network 3 and the second energy supply network 4 can thus also be determined. A further connection point 3b of the energy supply network 3 can be electrically coupled to a corresponding further connection point 2b at the first terminal 28 of the power converter 2.

[0042] The device 1 for monitoring the electrical current can, in particular, output a sensor signal from which a temporary peak value of the electrical current in the connection between the first energy supply network 3 and the power converter 2 can be determined. Additionally or alternatively, the device 1 for monitoring the current can also provide a sensor signal corresponding to a temporal average value of the electrical current between the first energy supply network 3 and the power converter 2. The provided sensor signals for the electrical current can be potential-free sensor signals, i.e., sensor signals that are galvanically isolated from the potential of the first energy supply network 3 and / or the second energy supply network 4.

[0043] Figure 2 shows a schematic representation of a basic circuit diagram of a device 1 for monitoring an electrical current in a power converter 2 according to one embodiment. As already described above, this device 1 for monitoring the electrical current can be provided, for example, in an electrical connection between a power supply network, for example the first power supply network 3, and a corresponding connection point of the power converter 2, for example a first connection point 2a of the first terminal 28 of the power converter 2.

[0044] The device 1 for monitoring the electrical current in the power converter 2 comprises a transformer 11 with a primary winding 11a and a secondary winding 11b. This primary winding 11a of the transformer 11 is provided in the electrical connection between the power grid and the power converter 2.

[0045] For example, a first connection point of the primary winding 11a can be electrically connected to the connection point 2a of the power converter, and a second connection point of the primary side 11a of the transformer 11 can be electrically connected to the corresponding connection point 3a of the first power supply network 3. In such a configuration, the primary winding 11a of the transformer 11 of the device 1 for monitoring the electrical current in the power converter 2 can be energized, for example, according to the switching behavior of the switching elements 21 and 22 in the power converter. The device 1 for monitoring the electrical current in the power converter 2 further comprises a switching element 12. This switching element 12 can be provided between a first connection point of the secondary side 11b of the transformer 11 and a reference potential (GND).The switching element 12 can be implemented, for example, by a series connection of two complementarily arranged semiconductor switching elements 12a and 12b. For example, the semiconductor switching elements can be MOSFETs or bipolar transistors with an insulated gate connection. In principle, however, any other suitable switching elements are also possible. If the switching element 12 is implemented by multiple switching components 12a, 12b, the multiple switching components 12a, 12b can be opened or closed using a common control signal. The switching element 12 conducts current in both directions when it is closed and blocks current in both directions when it is open.

[0046] Furthermore, the device 1 for monitoring the electrical current in the power converter 2 comprises a demagnetization device 13. This demagnetization device 13 is arranged in parallel with the secondary winding 11b of the transformer 11. In other words, a first connection point of the demagnetization device 13 is connected to the first connection point of the secondary side 11b, and a second connection point of the demagnetization device 13 is connected to a second connection point of the secondary side 11b of the transformer 11. The demagnetization device 13 can, for example, comprise a series circuit of two oppositely arranged Zener diodes 13a, 13b.Thus, an electric current can flow through the demagnetization device 13 if an electric voltage between the two connection points of the demagnetization device 13 exceeds a predetermined limit voltage corresponding to the dimensioning of the Zener diodes 13a, 13b. In this way, when the switching element 12 is open, an electric current can flow through the demagnetization device 13 to demagnetize the windings in the transformer 11. A first electric resistor R1 is provided between the reference potential and the second connection point of the secondary winding 11b of the transformer 11. Furthermore, a low-pass filter 14 can be provided in parallel with this first resistor R1. This low-pass filter 14 can be implemented, for example, by a combination of an electric resistor R2 and a capacitor C1.

[0047] For the operation of the device 1 for monitoring the electrical current in the power converter 2, the switching element 12 or the semiconductor switching elements 12a, 12b in the switching element 12 are controlled synchronously with the clocking in the power converter 2. In particular, the switching element 12 is closed when the primary side 11a of the transformer 11 is energized, i.e., when an electrical current flows between the first energy supply network 3 and the power converter 2. For this purpose, the control signals for the switching element 12 can be generated, for example, from the corresponding switching signals in the power converter 2, in particular from the gate control signals in the power converter 2.

[0048] With such a clocked switching behavior of the switching element 12, a voltage signal is present across the first resistor R1 in the device 1 for monitoring the electrical current flow, which corresponds to the electrical current through the primary winding 11a of the transformer 11 and thus to the electrical current between the first energy supply network 3 and the power converter 2. Thus, for example, the peak value of the electrical current in the power converter 2 can be determined from this signal. Furthermore, a voltage value corresponding to an average value of this electrical current is present at the node between the second electrical resistor R2 and the capacitor C1 of the low-pass filter 14.

[0049] During the time intervals in which the primary side 11a of the transformer

[0050] 11 is not energized, the switching element 12 is open. In these

[0051] At certain time intervals, an electric current can flow through the demagnetization device 13 to reduce the magnetization in the transformer 11. In this way, possible DC voltage offsets can be compensated.

[0052] The circuit configuration described so far already makes it possible to provide a sensor signal for positive electrical currents, i.e., electrical currents from the connection point 3a of the first energy supply network 3 toward the corresponding connection point 2a of the power converter 2. In order to be able to provide sensor signals with a positive output voltage even with the current direction reversed, for example, during inverse operation of the power converter 2 for energy transmission from the second energy supply network 4 to the first energy supply network 3, a reference voltage source 15 can be provided in the device 1 for monitoring the electrical current flow. This reference voltage source 15 can provide a voltage offset, in particular an adjustable voltage offset.The reference voltage source 15 can be coupled, for example, via a resistor divider with the series-connected electrical resistors R3 and R4 to the node K1, at which the second connection point of the secondary side 11b of the transformer 11 is located with the corresponding connection point of the first resistor R1. With such a configuration, a sensor signal can be provided at the node at which the two resistors R3 and R4 of the resistor divider are electrically connected to one another. This sensor signal corresponds to the current flow during the energization of the primary side 11a of the transformer 11, and from which the peak value of the electrical current in the power converter 2 can thus be derived.Furthermore, the reference voltage source 15 can be connected via a fifth resistor R5 to the low-pass filter 14, in particular to the node at which the second resistor R2 is connected to the capacitor C1 of the low-pass filter. Thus, a sensor signal can be provided at this node which corresponds to an average value of the current to be monitored in the power converter 2. Figure 3 shows a schematic representation of the time profiles of the control signal for the switching element 12, the current profile through the primary side 11a of the transformer 11 and the resulting sensor signals. The upper diagram I shows the control signal U_CTL for opening or closing the switching element 12. This control signal U_CTL can, as already described, be obtained, for example, in accordance with the gate control signals of the power converter 2.

[0053] Diagram II below shows the current curve l_PR IM through the primary side 11 a of the transformer 11. During the periods when the primary side 11 a of the transformer 11 is not energized, the switching element 12 is open. The current flows in both positive and negative directions. The negative component of the current in this time interval must also be measured by the measuring resistor R1 so that no offset occurs in the mean value measurement, particularly at very low output currents from the power converter 2. Passive rectification can lead to an offset error in the measurement because the negative current component is not measured in half-wave rectification or is measured incorrectly, i.e. as a positive value, in full-bridge rectification. With the bidirectional switch 12 proposed here, the current is measured correctly in both directions and therefore no offset can occur in the mean value measurement.

[0054] Diagram III below shows the profile of the sensor voltage U_MEAS as it results when using an offset voltage from the reference voltage source 15. The reference voltage source 15 and / or the corresponding resistors R3, R4, and R5 can be adjusted such that, even with a maximum expected negative current, i.e., with a power flow from the second energy supply network 4 to the first energy supply network 3, a negative sensor voltage U_MEAS is avoided. The resulting voltage offset or zero line, i.e., the sensor voltage U_MEAS, which corresponds to a zero electrical current to be monitored between the first energy supply network 3 and the power converter 2, can be determined, for example, during an initialization phase.

[0055] At the connection point l_AVG, which is coupled to the low-pass filter 14, a sensor signal can thus be provided which corresponds to an average value of the electrical current to be monitored in the power converter 2. Additionally or alternatively, a sensor signal can be provided at the connection point l_PK, from which a peak value of the electrical current to be monitored can be derived. The provided sensor signals can be used for any application, such as control or an emergency shutdown when a predetermined threshold value for the electrical current is exceeded. The provided sensor signals are, in particular, voltage signals which are galvanically isolated from the power converter 2.

[0056] Figure 4 shows a flowchart that may underlie a method for monitoring an electrical current in a power converter 2 according to one embodiment. The method can be applied, for example, to the previously described power converter arrangement or a suitably modified power converter arrangement. In step S1, the switching element 12 is opened alternately during step S1a, and the switching element 12 is closed in step S1b. The switching element 12 is closed when the primary side 11a of the transformer 11 is energized, and the switching element 12 is opened when the primary side 11a of the transformer 11 is not energized.

[0057] In step S2, a first voltage signal can be provided that corresponds to a peak value of the electrical current to be monitored in the power converter 2. Additionally or alternatively, a second voltage signal can be provided that corresponds to an average value of the electrical current to be monitored in the power converter 2.

[0058] In summary, the present invention relates to the monitoring of an electrical current in a power converter, for example a

[0059] DC-DC converter. For this purpose, a transformer is provided, which is coupled into a current path of the power converter on the primary side. On the secondary side of this transformer, sensor signals can be provided that correspond to the average and / or peak value of the current flow to be monitored. For this purpose, an electrical

[0060] The connection between the secondary side of the transformer and the sensor signal outputs is opened when the primary side of the transformer is not energized. During these time intervals, the transformer can be demagnetized to compensate for a DC offset in the current being monitored.

Claims

Claims 1 . Device (1) for monitoring an electrical current in a power converter (2), wherein the power converter (1) is designed to be coupled to a first energy supply network (3) at a first connection (28) and to be coupled to a second energy supply network (4) at a second connection (29), wherein the device (1) comprises: a transformer (11) which is electrically coupled to a connection point (2a) of the first connection (28) of the power converter (2) at a first connection point of a primary side (11a) of the transformer (11) and is electrically coupled to a connection point (3a) of the first energy supply network (3) at a second connection point of the primary side (11a);a demagnetization device (13) arranged between a first connection point and a second connection point of a secondary side (11b) of the transformer (11), and designed to conduct an electrical current between the first connection point and the second connection point of the secondary side (11b) of the transformer (11) if an electrical voltage between the first connection point and the second connection point of the secondary side (11b) of the transformer (11) exceeds a predetermined threshold value; a switching element (12) arranged between the first connection point of the secondary side (11b) of the transformer (11) and a reference potential; wherein the device (1) is designed to provide a first voltage signal (l_PK) from which a peak value of the electrical current to be monitored in the power converter can be derived, and / or to provide a second voltage signal (l_AVE) which corresponds to an average value of the electrical current to be monitored in the power converter (2).

2. Device (1) according to claim 1, wherein the switching element (12) is designed to be closed when the primary side (11a) of the transformer (11) is energized, and is designed to be opened when the primary side (11a) of the transformer (11) is not energized.

3. Device (1) according to claim 1 or 2, wherein the switching element (12) is designed to be controlled using a control signal of the power converter (2) 4. Device (1) according to one of claims 1 to 3, with a first measuring resistor (R1) which is arranged between the reference potential and the first connection point of the secondary side (11 b) of the transformer (11).

5. Device (1) according to one of claims 1 to 4, with an electrical low-pass filter (14) which is arranged between the reference potential and the first connection point of the secondary side (11 b) of the transformer (11).

6. Device (1) according to claim 5, comprising a reference voltage source (15) which is designed to provide an adjustable offset voltage, wherein the reference voltage source (15) is electrically coupled via a voltage divider (R3, R4) to the second connection point of the secondary side (11 b) of the transformer (11) and / or via a second resistor (R5) to an output connection point of the low-pass filter (14).

7. Device (1) according to one of claims 1 to 6, wherein the switching element (12) comprises two complementarily arranged semiconductor switching elements (12a, 12b) connected in series.

8. Device (1) according to one of claims 1 to 7, wherein the demagnetizing device (13) comprises two Zener diodes (13a, 13b) arranged oppositely in series.

9. A power converter arrangement, comprising: a power converter (2) configured to be coupled to a first power supply network (3) at a first terminal (28) and to be coupled to a second power supply network (4) at a second terminal (29), and a device (1) for monitoring an electrical current in the power converter (2) according to any one of claims 1 to 8.

10. Power converter arrangement according to claim 9, wherein the power converter (2) comprises at least one further switching element (21, 22, 23, 24) which is controlled by a control signal with a predetermined clock rate, and wherein the switching element (12) of the device (1) for monitoring an electrical current in the power converter (2) is controlled using the control signal for the further switching element (21, 22, 23, 24) in the power converter (2).

11. Method for monitoring an electrical current in a power converter (2) of a power converter arrangement according to claim 9 or 10, wherein the switching element (12) in the device (1) for monitoring the electrical current in the power converter (2) is alternately closed is opened when the primary side (11a) of the transformer (11) is energized and the switching element (12) in the device (1) for monitoring the electrical current in the power converter (2) is opened when the primary side (11a) of the transformer (11) is not energized; and wherein a first voltage signal (l_PK) is provided, from which a peak value of the electrical current to be monitored in the power converter (2) can be derived, and / or a second voltage signal (l_AVE) is provided, which leads to an average value of the electrical current to be monitored in the power converter (2) corresponds.

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